Pass-gate multiplexers are widely used in high-speed processors. Undetected faults on pins (or nodes) of certain circuits can cause computational errors. The faults at the select pins (or nodes) of such circuits can cause high-impedance (Z) output states, which cannot be detected using a tester. Undetected faults on pins (or nodes) of such circuits can prevent us from distinguishing good chips from faulty chips. It is desirable to detect all faults in circuits to meet ultra-low defective parts per million rates (DPM), typically less than 50, for example, for circuit in automotive industry. Due to large-scale usage of the pass-gate multiplexer's in high-speed circuits, coverage loss due to these undetected faults is large and must be solved to meet the ultra-low defective parts per million rates (DPM) criteria.